The present invention relates to an observation optical system, such as a binocular, a monocular or the like, provided with a hand-vibration compensation system.
Recently, observation optical systems provided with hand-vibration compensation systems for compensating trembling of image due to the hand-vibration have been developed. One example of the hand-vibration compensation system for a binocular is constructed such that a hand-vibration compensation optical system including compensation lenses is provided within an optical path of each of a pair of telescopic optical systems of the binocular. Such compensation lenses are moved in a direction perpendicular to the optical axis of each telescopic optical system. Specifically, in such a type of the compensation system, two compensation mechanisms are generally provided, which are:
(1) a mechanism for moving the compensation lenses in a vertical direction; and PA1 (2) a mechanism for moving compensation lenses, which are also provided within the optical paths of the telescopic optical systems, in a horizontal direction.
For the mechanism which moves the lenses in the vertical direction, it is necessary to change a response speed and/or voltage or electrical current for an actuator, depending on whether the lenses are moved in a direction of the gravity or in the opposite direction. In other words, controlling of the mechanism for moving the lenses should be changed when the lenses are moved in the vertical direction, and accordingly controlling is relatively complicated. Further, such a mechanism is required to have a driving device which has a relatively large torque in order to move the structure with resisting the gravity, and a relatively large battery for supplying sufficient power to such a driving device. Therefore, the conventional compensation mechanism becomes relatively large.
As a hand-vibration compensation device for a camera, which prevents blur of image on a film due to the hand-vibration, there has been known a device in which the compensation optical system is driven-along two different axes each of which does not coincide with a direction of the gravity. However, the optical system of the camera is generally designed with reference to sides of a picture frame, i.e., the vertical and horizontal directions, and therefore, it is not preferable to drive the compensation lenses in the directions which do not coincides with two sides of the picture frame of the camera, especially when compensation characteristics is to be changed in accordance with panning and/or tilting of the camera, and control thereof is also complicated.
With use of a variable angle prism, it is possible to avoid affection of the gravity. However, producing the appropriate variable angle prism is very difficult and expensive, and further, controlling of such a compensation mechanism is relatively difficult.